Automatic test equipment such as used, for example, in testing aircraft engine and/or flight parameters uses DC stimuli signals which must be generated with a high degree of accuracy. Accordingly, apparatus for generating said stimuli signals should include signal measurement and self-calibration features.
Prior to the present invention, calibration means for apparatus of the type described required precision analog to digital converters for these purposes and a correction was applied by measuring a reference voltage error and offset. This arrangement has, among others, the disadvantage of not correcting for output non-linearity. The present invention overcomes the disadvantages of the prior art by amplifying existing errors and measuring the errors using conventional analog to digital converters. The measured errors are reduced via a least square error reduction arrangement, based on a minimum number of error measurements to accomplish the required calibration. A central processing unit (CPU) determines the offset and gain correction to be applied.